Circuit breaker devices have been known heretofore and have been used as circuit protective devices in aircraft and the like because of their resettability. Unlike fuses which are destroyed on an overload and which have to be replaced, circuit breakers which trip in response to an overload can be used to reclose the protected circuit once the overload condition no longer exists. Another advantage over fuses is that aircraft circuit breakers of the remote control type are equipped with manual actuation and indication capability which indicates the open/close command sent to the remotely located breaker device by the position of the indicator control unit (I/CU) operating lever, which indicator control unit is located in the cockpit or flight deck of the aircraft. In a crowded flight deck where circuit breakers are found by the hundreds, it is often very difficult to locate each device and to control it manually. Of course, it is practically impossible to visually monitor all the indicator levers and to be able to locate an overload trip the moment it occurs. This task is more suitable for microprocessors than for human beings. The microprocessors can rapidly scan all of the circuit breakers and compare their states to the commands in memory and initiate a warning and identification display when they differ. Instead of a huge switch board, a small key board and disp1ay unit could be used.
The electronic circuits of prior remote control circuit breakers (RCCB's) were very limited in their capabilities. The disadvantages inherent therein included at least the following. They were not intended or suited for computerized control. Entirely different operating circuits were required for single phase and three-phase devices. The single-phase devices involved the mechanical complexity of cutthroat contacts. They were subject to rapid cycling damage. They had limited noise immunity. Since they did not utilize three state signalling, they were subject to possible operating state ambiguity due to low voltage, welded contacts, false trip, etc. The three-phase device was subject to unnecessary coil current pulse during power-up. While the coil pulse durations were timed, such timing was not a function of contact transfer in the three-phase devices. And they involved the mechanical complexity of overload trip switch and linkage.